Officials in at least 14 states — Alabama, Arkansas, California, Colorado, Florida, Indiana, Kentucky, Louisiana, Maryland, Pennsylvania, Tennessee, Texas, Virginia, West Virginia — and Washington had posted warnings by 9:30 p.m. Some said the problem was sporadic while others said it was statewide or nationwide.
https://www.nytimes.com/2017/03/08/us/att-users-unable-to-call-911.html
FCC probes why AT&T customers could not call 911